home-network-k3s-impl/runbooks/kubevirt-launch-failed.md

# kubevirt-launch-failed — One or more VirtualMachineInstances are in the Failed phase

**Alert:** `KubeVirtVMLaunchFailing` (critical, 5m)
**File:** `platform/kubevirt/alerts.yaml`, group `platform-health.kubevirt`
**Expression:** `sum by (namespace) (kubevirt_vmi_phase_count{phase="Failed"}) > 0`

## What this means here

A VMI reached the `Failed` phase — a scheduling, launch or qemu failure. The IaaS path is broken for that
workload, which is why it is page-worthy even though the VM tier is deliberately **non-gating**
(`apps-vms` is `wait: false`, `dependsOn: platform-config`, because a VM's image import and in-guest
install are legitimately long-not-Ready).

What actually runs here: the `unifi` namespace holds the UniFi VM (rootdisk 40 GiB, Block mode on
`longhorn-vm`). **UniFi OS Server is not yet installed in the guest** — that is known, documented state,
not a launch failure.

**Live note, measured 2026-09-13:** `kubevirt_vmi_phase_count` returned **0 series** on prod. That metric
only exists while VMIs do, so this alert is currently evaluating against nothing. Confirm the real state
from `kubectl get vmi -A`, not from this alert's silence. (`kubevirt-prometheus-metrics` *is* a live scrape
job and `kubevirt_virt_api_ready_status` does publish, so the target is up — see
`/runbooks/kubevirt-control-plane`.)

### The three k3s-specific launch failures this platform already hit and fixed

Recorded from bring-up, and worth checking against any new VM definition because all three were
non-obvious:

1. **`containerDisk` requires the ALPHA `ImageVolume` feature gate**, which is off on k3s. The fix was to
   switch to a **CDI DataVolume on Longhorn** instead. A VM authored with `containerDisk` will not launch
   here.
2. **A UEFI image needs `firmware.efi`** set on the VM. Without it, boot fails.
3. **`useEmulation: true` silently forces TCG on KubeVirt v1.9** — it is set to `false` deliberately. A VM
   that appears to launch but burns a whole core per vCPU is this; it also degrades the Cilium datapath
   under sustained load.

Also recorded: a `virt-handler` certificate error seen during that work was **unrelated and cosmetic** —
do not chase it.
## Running the commands in this runbook

`kubectl` does not work on the operator workstation. The toolchain lives only in the pinned dev
container, and the host's `k3s-oidc` context hangs on a browser prompt once its token expires —
that hang is not the cluster being down. Every command below runs as:

    infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod get nodes'

Always pass `--context k3s-prod` explicitly. `dev.sh` merges BOTH clusters into one kubeconfig and
picks a current-context per invocation, and **that default has already changed once** — it was k3s-dev
until dev was decommissioned on 2026-09-13, and is k3s-prod now. A command that names its context means
the same thing next month as it does today; one that relies on the default does not, and the failure is
silent (it answers confidently about the other cluster). `CLUSTER=prod infra/devcontainer/dev.sh run
kubectl ...` selects it explicitly, and every invocation prints a banner naming the cluster it is about
to talk to — read it. Do not run two `dev.sh` invocations at once; they share one container and
interfere.

USE FULLY-QUALIFIED RESOURCE NAMES, ALWAYS. Three CRDs on this cluster register the kind `Backup`:
`longhorn.io/v1beta2`, `postgresql.cnpg.io/v1` and `velero.io/v1`. The bare short name resolves to
Longhorn's, which holds zero objects — so `kubectl get backup -A` prints **"No resources found"** on
a cluster holding 6 Velero backups and 27 CNPG backups. Verified on prod 2026-09-13. Reading that as
"the backups are gone" and acting on it turns a false negative into real data loss. Write
`backups.velero.io`, `backups.postgresql.cnpg.io`, `clusters.postgresql.cnpg.io`,
`settings.longhorn.io`, `volumes.longhorn.io`, `nodes.longhorn.io`.

Mutating kubectl (`apply`, `patch`, `annotate`, `rollout`) and `flux reconcile` are blocked for
agents here: every durable change goes through git (`git push origin main` **is** the deploy).
Where this runbook gives a mutating command it is for an operator, and it says so.

## First commands

Which VMI, in which namespace, and what phase:

```
infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod get vmi -A -o wide; echo; \
   kubectl --context k3s-prod get vm -A -o custom-columns=NS:.metadata.namespace,NAME:.metadata.name,STATUS:.status.printableStatus,READY:.status.ready'
```

The reason — the VMI status conditions and the launcher pod's events are where it is stated:

```
infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod -n unifi describe vmi unifi 2>&1 | sed -n "/Status:/,\$p" | head -60'
```

```
infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod -n unifi get pods -l kubevirt.io=virt-launcher -o wide; echo; \
   kubectl --context k3s-prod -n unifi describe pod -l kubevirt.io=virt-launcher 2>&1 | sed -n "/Events:/,\$p"'
```

Is the disk there? (A missing or still-importing DataVolume is the most common cause.)

```
infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod get datavolumes.cdi.kubevirt.io -A \
     -o custom-columns=NS:.metadata.namespace,NAME:.metadata.name,PHASE:.status.phase,PROGRESS:.status.progress; echo; \
   kubectl --context k3s-prod get pvc -A | grep -Ei "rootdisk|dv|unifi"'
```

Is nested virtualisation actually available on the node it was scheduled to?

```
ssh k3s-prod-1 'ls -l /dev/kvm; grep -c -E "vmx|svm" /proc/cpuinfo'
```

Is the storage class right for a live-migratable VM?

```
infra/devcontainer/dev.sh run bash -c \
  'kubectl --context k3s-prod get sc; echo; \
   kubectl --context k3s-prod -n longhorn-system get volumes.longhorn.io -o custom-columns=NAME:.metadata.name,ROBUST:.status.robustness | grep -v healthy'
```

And whether the KubeVirt control plane can act at all:

```
infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod -n kubevirt get pods'
```

## Likely causes, most likely first

### 1. The disk is not ready — a CDI import that has not completed or has stalled
The VM cannot start without its DataVolume. Go to `/runbooks/cdi-import-stuck`. The specific recorded
failure: the **3-replica default class failed the UniFi 60Gi import with insufficient storage /
`ReplicaSchedulingFailure`**, which is why a dedicated single-replica **`longhorn-scratch`** class exists
and is referenced by the CDI CR's `scratchSpaceStorageClass`.

### 2. The VM is authored in a way k3s does not support
The three items above: `containerDisk` without the ALPHA `ImageVolume` gate (use a CDI DataVolume),
missing `firmware.efi` for a UEFI image, or `useEmulation: true` forcing TCG. All are git changes to the
VM definition.

### 3. The cloud-init payload is too large or corrupted
Two precise traps. **KubeVirt caps inline `userData` at 2048 bytes** — the original rich cloud-init
exceeded it; `userDataSecretRef` was tried and reverted, and the shipped state is a minimal ~1.1 KB inline
payload. And: **`apps-vms` must NOT carry `postBuild.substituteFrom`** — Flux's envsubst rewrote `${...}`
inside the cloud-init and corrupted it (commit `da1f833`). *Do not restore substitution there for
consistency with the app waves.* If a VM stopped booting right after someone "tidied up" the Flux
Kustomizations, this is it.

### 4. It cannot be scheduled
No node with room, or a storage constraint. A live-migratable VM needs **`longhorn-vm`**: RWX,
**Block mode only** (migratable RWX is a raw block device, not the share-manager/NFS path), annotated
`storageclass.kubevirt.io/is-default-virt-class: "true"` — which is *not* the cluster default class.
A VM pointed at plain `longhorn` will not live-migrate.

### 5. The CDI importer cannot open the raw Block device
`nonroot-devices: true` is set on the k3s servers because the non-root CDI importer must open a raw Block
device that Kubernetes never chowns for it (commit `df5979f`). A permission error in the importer on a
Block PVC is this.

### 6. The KubeVirt control plane is down
Then nothing can launch. `/runbooks/kubevirt-control-plane`.

## When to escalate or stop

- **Scope it before escalating.** The VM tier is non-gating and does not affect the container platform.
  One failed VM is not a platform outage — but the UniFi VM is the home network's controller, so treat
  that one as user-visible.
- **Do not delete the VM or its DataVolume to "start clean".** A 60 GiB re-import is hours of I/O on disks
  that share a partition with the embedded etcd WAL, and that is the mechanism behind the 2026-09-07 node
  outage. Fix the definition, not the data.
- **Do not set `evictionStrategy: LiveMigrate` cluster-wide.** A blanket setting would **wedge drains**
  for RWO-disk VMs; it is per-VM on purpose.
- **Do not add `postBuild.substituteFrom` to `apps-vms`.** It corrupts cloud-init.
- Escalate for anything that needs a fresh image import during a storage incident, and for changes to the
  k3s server flags (`nonroot-devices`) — those are Ansible/operator work.

---
Source of truth: `runbooks/kubevirt-launch-failed.md`. Index: `/runbooks/`
Records: `DECISIONS-LOG.md` Session 7 (the three k3s-specific launch failures); commits `da1f833`
(cloud-init corrupted by envsubst) and `df5979f` (`nonroot-devices`); the `longhorn-scratch` /
UniFi 60Gi import finding.